Why two perfect display LUTs still don't match
Sensor, gamut, and white balance: the three reasons two correct LUTs produce two clips that look like they're from different planets.
The setup is familiar. A two-camera shoot. Both cameras tagged correctly: Sony FX6 in S-Log3, Canon C70 in C-Log3. Both display LUTs picked from the manufacturer's own pack: S-Log3 to Rec.709, C-Log3 to Rec.709. Drop the clips on the timeline.
They don't match. Not even close.
This is the most common color question new editors run into, and the answer is not "the LUTs are wrong." The LUTs are doing exactly what they were built to do. The mismatch lives in three places upstream of the LUT.
Reason 1. The sensor
The display LUT converts a LOG signal to a viewable Rec.709 image. What it does not do is correct for the camera's underlying sensor color.
Every sensor sees light slightly differently. The color filter array on a Sony sensor lets a different mix of wavelengths through than a Canon's. The on-sensor demosaic and downstream processing pipeline interpret those wavelengths into RGB triplets through math that is unique to each camera maker.
The display LUT works on the encoded LOG signal. It assumes the signal already arrived encoded correctly. It cannot reach back and rebalance the sensor's actual response.
So the FX6's S-Log3 to Rec.709 LUT is correct for an FX6, and the C70's C-Log3 to Rec.709 LUT is correct for a C70, and the two correct conversions still produce two slightly different pictures of the same scene. Because the two correct conversions started from two slightly different captures of that scene.
Reason 2. The gamut
LOG is not just a tone curve. It is a tone curve plus a color space (a "gamut"). S-Log3 lives in S-Gamut3.cine. C-Log3 lives in Canon Cinema Gamut. V-Log lives in V-Gamut. These are wider-than-Rec.709 spaces, each shaped slightly differently.
The conversion LUT does two jobs at once: roll the tone curve down to display range, and map the source gamut into Rec.709. Two different source gamuts produce two slightly different Rec.709 outputs even from identical-looking LOG.
The fix is not to use the same LUT on both cameras (that breaks the tone curve and shifts the picture). The fix is to acknowledge that the conversions are correct and then go match the results to each other after the conversion.
Reason 3. The white balance on set
This is the easiest one to forget and the largest source of visible mismatch when it happens.
Even with identical camera profiles and identical display LUTs, the operator's white balance choices on set move the file. A B-cam left on auto white balance drifts shot to shot. An A-cam locked to 5600K and a B-cam locked to 5200K produce two different captures of the same light. A clip exposed half a stop hotter than its companion comes out brighter and slightly more saturated, even after the display LUT.
White balance and exposure are the scalar corrections: temperature, tint, lift, gamma, gain. They are the easy ones to fix in Lumetri. The sensor and gamut differences above are the hard ones, because they are three-dimensional transforms of the color volume rather than single-axis nudges.
What this means in practice
The display LUT puts the picture into viewable range. It does not put two cameras in agreement. Those are two different jobs, and editors trying to do the second with the first end up pulling curves and HSL for hours.
The correct order:
- Display LUT first. Apply the manufacturer's own conversion LUT on each clip's Input LUT slot in Lumetri Color. This gets each camera into viewable space using the conversion the camera maker designed.
- Scalar correction next. White balance and exposure differences come out in Lumetri's Basic Correction. Temperature, Tint, Exposure, Saturation. Small moves, one camera at a time.
- Camera match last. Once both cameras are in viewable space with their scalar nudges, they still won't agree, and now is when a tool that handles the sensor/gamut difference earns its keep. That is the job MOVON is built for.
Where MOVON fits
MOVON sits after the display LUT and the scalar correction, in the camera-matching slot. It reads the displayable signal (post-LUT, post-WB) from the hero camera and from the cameras matched to it, and generates a custom 33³ .cube LUT that transforms each non-hero group's sensor/gamut into something that agrees with the hero's. Where this lands in the chain is covered at Where MOVON sits in your grading chain.
The shorter way to put the whole story: a display LUT converts a recording to a viewable image. A match LUT converts one viewable image to look like another. Two different jobs. Two different tools.
